Core traits and types for the Rhei HTAP engine.

rhei-core is the foundation crate of the Rhei workspace. Every other crate depends on it for shared abstractions. It deliberately has no dependencies on concrete database drivers so that it can be compiled quickly and used as a pure trait/type boundary.

Position in the HTAP pipeline

Client
  |
  v
HtapEngine  (crates/rhei)
  |-- QueryRouter  ──────────────────── routes SQL to OLTP or OLAP
  |-- OltpEngine   ──────────────────── transactional reads/writes
  |-- OlapEngine   ──────────────────── analytical queries
  |-- CdcConsumer  ──────────────────── polls change-data-capture events
  +-- SyncEngine   ──────────────────── applies CDC events to OLAP

Key types